Reaction of the ligand 2, 2′‐diamino‐4, 4′‐bithiazole (DABTZ) with Zn(ClO4)2, CdCl2, and Hg(SCN)2 gives complexes with composition [Zn(DABTZ)2](ClO4)2, [Cd(DABTZ)2Cl2], and [Hg(DABTZ)(SCN)2]. The complexes were characterized by elemental analyses and infrared spectroscopy. The crystal structure of the [Hg(DABTZ)(SCN)2] was determined by X‐ray crystallography. The complex is built up of a monomeric Hg(SCN)2 unit with one 2, 2′‐diamino‐4, 4′‐bithiazole ligand coordinated to the Hg atom via the two N atoms giving rise to a five‐member chelate ring in a distorted tetrahedral environment. There is π‐π stacking interaction between the parallel aromatic rings belonging to adjacent chain as planar species in which the mean molecular planes are close to parallel and separated by a distance of ∼ 3.5Å, close to that of the planes in graphite. The coordinated 2, 2′‐diamino‐4, 4′‐bithiazole molecule is involved in hydrogen bonding acting as hydrogen‐bond donors with N atoms from the SCN ligand as potential hydrogen‐bond acceptors. The hydrogen bonding yields infinite chains parallel to the crystallographic vectors a and b. Each molecule is bonded to three neighbours. Both amine H atoms are hydrogen bonded to N atoms.

Source of materialTo a solution of pyridine-2-carbaldehyde thiosemicarbazone ligand in methanol (10 ml) was added a aqueous solution of zinc nitrate and excess of sodium Perchlorate. The reaction mixture was stirred for 10 h at room temperature and left in room temperature for five days. The yellow crystals were filtered off, washed with cold methanol and ether and dried in vacuum over P4O10 (mp 488 K; yield 60%). Elemental analyses were consistent with the stiochiometry C7H9CIN4O4S. Melting points were measured on an Electrothermal 9100 apparatus and are uncorrected. DiscussionThe ligand of pyridine-2-carbaldehyde thiosemicarbazone possess a wide range of biological activity depending on the parent aldehyde or ketone. Heterocyclic thiosemicarbazones are important because of their possible beneficial biological activity. In the last twenty years, the metal complexes derived from this ligand have drawn some attention. In most of cases, the ligand is tridentate binding to the metal through the N-pyridine, N-azomethine and S atoms. The chemistry of complexes of this ligand markedly depends on the kind of transition metal ions. In the course of our studies of the syntheses and reactions of amidic and thioamidic derivatives ligands with zinc(II) salts [1,2], we have isolated an interesting adduct of pyridine-2-carbaldehyde thiosemicarbazone and perchloric acid. The adduct structurally characterized by X-ray crystallography.

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